value = None
print(value is None)
value1 = 2
value2 = 2
print(value1 is value2)
# 两个包含城市名称的列表（例如内蒙古城市）
cities1 = ["呼和浩特", "包头", "鄂尔多斯"]
cities2 = ["呼和浩特", "包头", "鄂尔多斯"]
# 引用 cities1
cities3 = cities1
# 判断是否为同一对象
print(cities1 is cities2)
print(cities1 is cities3)
print(cities1 is not cities3)

